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Managing heat stress in pastured meat chicken production.

With meat chickens (broilers), protection from the elements not only means sun and rain, but also a place of refuge during hot weather.

Our featured image shows modern fast growing strains of meat chickens known as broilers.

These birds suffer increased mortality rates during periods of hot weather, due to the excessive muscling and fat they carry around their breast and body cavity, particularly if their body weight exceeds approximately 1.5 kg. Any structure that houses them should ideally be able to keep the temperature below 300C, not an easy task with our hot summers in most parts of Australia. It is obvious therefore, that the chicken farmer who raises these strains must be extra vigilant in the summer.

It is worth noting that the intensive chicken industry aim to maintain a temperature between 21-240C inside their sheds. These producers rely on state-of-the-art technology to maintain these temperatures, and modern broiler sheds are quite complex in their environmental management systems. Even large-scale free range and organic chicken producers employ temperature controlling mechanisms inside their large fixed sheds, however not to the same level because genuine free range birds need easy and constant access to the range area.

For small-scale meat chicken producers who use portable shelters, it is largely unviable to employ these same technologies, so a different approach needs to be taken. If you live in an area with summer temperatures consistently above 350C, then you probably will not be able to raise modern strains of broilers all year round, however, the following principles may help relieve some of their stress.

Shelter DesignWhen designing portable shelters for pastured meat chicken production, the welfare needs of the chicken should always take precedent over land regeneration goals.

All shelters must comply with the The Model Code of Practice for the Welfare of Animals – Domestic Poultry clause 6.3 which states:

“The housing facilities must be designed to ensure adequate air-flow and temperature control at maximum stocking densities when birds cluster at night or during extreme weather conditions.”

Portable shelters are no exception, and must be designed to maximize ventilation and air-movement, without exposing the birds to the negative effects of sun, rain and draughts. It is the farmer’s responsibility to ensure their shelters are strong enough to withstand, and protect birds during extreme weather conditions.

Pictured above is the latest shelter in use at ‘Kildare’. The shutters are fully adjustable for varying weather conditions. Netted frames on a winch system allow us to give the birds’ instant access to outdoors and protect them from predators at night. They also allow us to keep the shutters open for air-flow on hot summer nights. The height allows comfort for the farmer, and when combined with cross-ventilation it provides improved temperature control during hot weather. It measures 9 x 3m, and accommodates up to approx. 250 birds at processing age.

Flooring ConsiderationsThe most vulnerable period during a heat wave is when nights stay hot. Birds tend to build up body heat during extended periods of hot weather. If their body temperature can be reduced during the evening, they will have a far greater ability to survive periods of extreme heat.

Assuming you lock the birds in their shelter at night for added predator protection, there must be enough space to allow the birds to cool down in the evening, (approx.10 birds per square metre floor space ).

A bird’s natural instinct is to get off the ground, i.e. ‘roost’ at night. Whilst modern strains of broilers now become heavy very quickly, and aren’t able to roost the way lighter strains of chickens can, it is still important to design a shelter that does not resign them to roosting directly on the ground. We recommend a flooring or bedding system that offers raised roosting comfort.

LitterLitter (wood shavings) on the floor of your pen can contribute to the birds’ well-being. If you provide a good depth of dry, friable litter, the birds will use it to keep cool by working their way down and spreading wings and feathers to expose flesh to the cooler material. Spraying the shavings with a very fine spray of water will be even better.

Litter does however add another tier of complexity to the design of a portable shelter, and this system only works well on reasonably level ground. Litter provides comfort and carcass protection, so long as the litter is kept dry and friable, and this is greatly influenced by ventilation, stocking density and management.

Plastic SlattingThere are ready-made modular slats on the market that are specifically designed for heavy strains of poultry. As well as allowing extra air-flow during hot weather, it also keeps birds drier during wet weather, and enables the excrement to fall through. This system is particularly useful when, for example, a farmer needs to place the shelter in un-level terrain.

Access to shadeShade is essential for the birds’ welfare in the summer. Shelters should be designed to provide as much as possible, and should be situated under or near the shade of trees or shade structures wherever possible.

OrientationAll animal shelters should be oriented with openings facing to the north, with the ability to close the west, south, and east openings for protection during inclement weather.

Shape and WidthIn very broad terms, a length to width ratio of 4:1 in a growing shelter allows optimal air-flow and ventilation management. This a guide only, and farmers should consider other factors including portability, material sizes and existing farm infrastructure.

HEAT WAVE ACTION PLANPlanning ahead is vital, as early or sudden heat waves are more dangerous than those which occur after several warm periods because birds become acclimatised to higher temperatures.

When the temperature rises further, birds can survive, but you must be vigilant.

Remember to move very slowly and cautiously through the birds to avoid extra stress, and try to do the majority of your husbandry work in the early morning and late evenings.

Water Management
Keeping a reliable, clean, “COOL” source of water available to poultry is essential to help the birds cope with high temperatures. BIRDS WILL NOT DRINK WARM WATER.

Make sure all drinkers are kept clean and functioning correctly, and not blocked in any way. Avoid having permanent water pipes and hoses near the ceiling of the shelter, hot western walls, and lying above the ground, where the water will gain extra heat.

Water lines in which the water has become warm should be drained to allow cooler water to reach the drinkers.

Sufficient drinkers need to be available to accommodate all the birds at the one time, and they must also be adjusted to the right height for the birds and kept in the shade.

If severe heat waves are predicted, consider an emergency source of water should the primary water source fail. You may want to have a supply of ice blocks on hand to cool the water in the mid afternoon when temperatures are extremely high and the flock’s resilience is low.

Because the birds excrete electrolytes during periods of heat stress, electrolytes can be added to the drinking water to replace those that are lost and to stimulate water consumption.

If a heat waves continues for more than one or two days, the birds get exhausted and their appetite is diminished, water soluble vitamins are also beneficial to replace nutrients quickly and help revive the bird.

Range Management
Grass cover on the grounds surrounding the poultry shelter will reduce the reflection of sunlight into the house. Vegetation should be kept trimmed to avoid blocking air movement. Hosing the ground directly around the house will also help, as will directly spraying the birds, but this works best if there is air movement. Care needs to be taken to avoid excessively wetting the ground and the birds and creating high humidity which will make the birds more uncomfortable.